This section is a step-by-step tutorial in how to plot the ERPs following target trials, standard trials and their difference at all electrode locations organized in a scalp topography. This allows you to visually compare temporal and scalp distribution of the ERP, which can give you a good idea of your data. If all goes well, you should obtain a plot like this:

See the EEGLAB wiki for more information (scroll down to “the EEGLAB tutorial outline”).

Because EEGLAB tends to get slower the more data sets are loaded, especially with large data files, you could delete data sets you are not going to use by selecting Edit > Delete dataset(s), entering its data set number and clicking OK.

Extracting the epochs: Tools > extract epochs

click the '…' button next to 'Time-locking event type(s)' and select StimulusBegin.

Choose an appropriate start and end window for the epochs, such as '0 0.8'. These values need to be entered in seconds.

The word 'epochs' is automatically added behind the name of the data set from which you extracted the epochs. Click OK if you agree with the name for the new data set.

If you want to save the new data set to disk, in the next window “pop_newset()” you can check the box 'Save it as file', enter a file name and click OK. If not, click OK as well without checking the box.

Epoch baseline removal: to make sure that the P300s of different electrodes are compared to a similar baseline signal, we subtract the average signal of 0 to 100 ms from the whole epoch (0 to 800 ms). Enter the baseline latency range '0 100'.

Load the electrode locations: this is required if you want to see the ERPs of all electrodes in a scalp topographic fashion. To do this, go to: